When the temperatures of the gas being filtered are extremely high, say above 1400 degrees F., it has been the practise to manufacture the internal parts of the filter from ceramic materials. Temperature gradients in ceramic materials are known to cause cracking, and in the case of large diameter tube sheets where the peripheral portions are in proximity to the ambient while the central portions are exposed only to the hot gasses being filtered, avoidance of cracking due to the tendency of the peripheral portions of the tube sheets to be cooler than the central portions has become a major objective in the design of hot gas filters.